I'll leave it to the people who know to tell you whether the lifters are
solid or hydraulic.

If they are hydraulic (and it is true: hydraulic lifters have no
adjustment), I recommend you try the simple things first. This is one of the
few situations in which I recommend an engine flush. Follow the directions
exactly, ending with an oil change.  Again breaking with normal
recommendations, I recommend you fill with regular "dino" oil (rather than
synthetic, just because the purpose doesn't justify the extra cost of
synthetic) in the lightest grade approved for the car - consult the owner's
manual. Drive the car for several days - if the tap persists, do the engine
flush again. If still no good after a week or so, time for a pro to replace
the lifter. It is usually a good idea to replace all the lifters in that
half of your V6 - the lifters aren't usually very expensive compared to the
labor required to get to them and all the lifters have been in the same
environment..

Collapsed lifters are usually an indication of sludge fouling, caused by
neglect of the oil changes.

Mike

Generally speaking the hydraulic lifters on a 90 Legend do not require
regular adjustment. However as the valves and valve train wear it is
possible for the adjusters to run out of travel. This will cause valve
tapping. The adjusters can be recentered, so that they are once again
in the middle of their adjustment range.

My 90 Legend had this problem and recentering the exhaust adjusters
cured it.

Your car could also be suffering from a sludge buildup or have a
wornout adjuster. Best of luck.

Exhaust valves are adjustable but the noise usually comes from valve train
wear due to sludge buildup. The exhaust pushrods will wear on the ends
causing them to mushroom which increases the clearance in the valvetrain.
Usually only proper way to fix is to replace components that are worn. Good
Luck

David Short
Acura God